The above-named professional personnel propose to collaborate with other members of CCSG as well as with other members of other cooperative study groups, in research on leukemia, malignant solid tumors and closely related disorders in children. The chief purpose of the CCSG is to cooperate in several aspects of research in malignant disease in children (i.e., the natural history, epidemiology) and in particular to develop, evaluate and improve methods of diagnosis, prognosis and treatment of malignant disease in children. Special emphasis will be placed on the study of new combinations and new schedules of already established chemotherapeutic agents as well as on the evaluation of new anti-cancer agents and new modalities of therapy. The Principal Investigator is Chairman of the Histiocytosis Committee and has recently received approval by CIB of a new protocol designed to study this disorder in depth with particular attention to clinical and histologic features of prognostic significance, improved therapy and comprehensive immunologic evaluation. The prognostic significance of certain clinical features developed by CCSG has been tested and acclaimed by other chemotherapy groups.